Variable transformer with winding holding core housing



F. l. ELLIN April 25, 1967 VARIABLE TRANSFORMER WITH WINDING HOLDING CORE HOUSING 2 Sheets-Sheet 1 Filed May 19, 1965 April 25, 1967 F. 1. ELLIN 3,316,517

VARIABLE TRANSFORMER WITH WINDING HOLDING CORE HOUSING 2 Sheets-Sheet 2 Filed May 19, 1965 United States Patent VARIABLE TRANSFORMER WITH WINDING HOLDING CORE HOUSING Fredrick I. Ellin, Skokie, Ill., assignor toConsolidated Electronics Industries Corp., Skokie, Ill., a corporation of Delaware Filed May 19, 1965, Ser. No. 456,978 Claims. (Cl. 336-149) This invention relates generally to the electrical arts and'more particularly to variable transformers and analogous devices.

In the past, variable transformers were made with a pair of insulating paper sleeves for separating the magnetic core and the winding of conductive wire. These sleeves were telescoped over each other, and the outer sleeve carried the terminals for the unit. Rigid end discs were provided with grooves for positioning the winding, and varnishing or potting was frequently employed. Moreover, the variable transformer constructions of the prior art were not amenable to ready change of drive shaft. Thus, variable transformers have been heretofore unduly complicated to assemble.

The present invention therefore takes as its principal object the overcoming of these disadvantages of the prior art arrangements and the provision of a new and improved construction for variable transformers and the like.

Another object of the present invention is to provide a construction for variable transformers and the like which is adapted for assembly exclusively by mechanical coupling and fastening arrangements and which thereby avoids wet assembly procedures such as adhesive bonding, potting, and thermal or oxidative curing.

Still another object of the invention is to provide a rigid, prefabricated separator housing for the magnetic core of variable transformer units and the like.

And still another object of the invention is to provide a novel drive shaft assembly for variable transformer units and the like.

And a further object of the invention is to provide a construction for variable transformers and the like which is characterized by economy of manufacture and the avoidance of special manufacturing tools and equipment.

These and other objects and features of the invention will become more apparent from a consideration of the following descriptions.

In accordance with one feature of the invention, a variable transformer is constructed to comprise an annular magnetic core, an electrical winding on the core, and an insulative housing between the core and the winding. This insulative housing includes a pair of similar cuplike housing elements that are aligned with their open ends in confronting relationship to form an enclosure for the magnetic core.

In order that the principles of the invention may be readily understood, a single embodiment thereof, but to which the application is not to be restricted, is shown in the accompanying drawings wherein:

FIG. 1 is a front elevational view of a variable transformer unit constructed in compliance with the invention;

FIG. 2 is a rear elevational view of the transformer unit of FIG. 1; 1

FIG. 3 is an exploded perspective view of the transformer unit of FIG. 1;

FIG. 4 is an exploded perspective view of the drive shaft assembly of the transformer unit of the invention;

FIG. 5 is an enlarged, central sectional view taken substantially along the line 55 of FIG. 1.

FIG. 6 is a fragmentary central sectional view taken substantially along the line 6--6 of FIG. 5; and

3,316,517 Patented Apr. 25, 1967 FIG. 7 is an exploded perspective view of the assembly constituting the magnetic core, the insulative housing therefor and the cooperating terminal board.

Referring now in detail to the drawings, specifically to FIGS. l-3, a variable transformer unit of the autotransformer type is indicated generally by the reference numeral 10. The transformer unit 10 comprises a core and winding assembly 12, a drive shaft and contact arm assembly 14, and a dial and mounting plate assembly 16.

Turning to a consideration of FIGS. 5 and 7, the core and winding assembly 12. is seen to comprise an annular magnetic core 18 that is fabricated in the shape of a cylinder having an axial bore 20. The assembly 12 also includes an electrical winding 22 that, in the illustrated embodiment, takes the form of a suitable length of insulated, electrically conductive wire that is wound generally helically about the core 18. In accordance with an important feature of the present invention, a rigid, insulative housing 24 is disposed between the core 18 and the winding 22. In addition, the insulative housing 24 comprises a pair of identical, cup-like housing elements 26 which are best seen in FIG. 7; and these housing elements are aligned with their open ends in confronting relationship in order to form an enclosure for the core 18. Each of the housing elements 26 includes an annular base plate 28, a first tubular wall 30 extending from the base plate 28 at the outer edge thereof, and a second tubular wall 32 extending from the base plate 28 at its inner edge. The tubular walls 30 and 32 are disposed in coaxial relationship to cooperate with the base plate 28 in defining an encasement for totally enclosing one end of the annular core 18. The tubular wall 30 is sized and dimensioned to slip over the outside of the annular magnetic core 18; and similarly, the inner tubular wall 32 is sized and dimensioned to slip telescopin-gly inside the bore 20 of the magnetic core 18. Additionally, the respective lengths of the tubular walls 30 and 32 are related to the axial length of the magnetic core so that the two housing elements 26 fit over the magnetic core 18 and abut each other to form an encasement totally enclosing the core. Because the housing elements 26 are intended to prevent electrical contact between the winding 22 and thecore 18, these housing elements are fabricated from a material having appropriate, electrically insulating properties. Resinous plastics materials have proved eminently useful in this regard and, in addition, permit fabrication of the housing elements in an economical molding operation.

It has also proved advantageous to fashion certain regions of each housing element 26 with a series of generally radially aligned grooves to guide and position the wire used for the winding 22. As is shown in FIG. 7, one region with such a series of grooves is advantageously provided on the external edge at the juncture between the tubular wall 32 and the base plate 28, this series of grooves being indicated by the numeral 34. cooperatively, a second series of such grooves is provided on the external surface of the base plate 28 closely adjacent its juncture with the outer tubular wall 26, this series of grooves being indicated by the numeral 36. The grooves 36 are generally spirally aligned with the grooves 34, and it has proved convenient to dispose the grooves 36 on a raised circular formation 38.

As will be recognized, the winding 22 serves to preserve the housing elements 26 in axially abutting relationship after it has been applied; and in accordance with another feature of the present invention, means are provided for locking the housing elements 26 against relative rotational movement. In the llustrated embodiment, these means comprise radial formations 40 which are fashioned as integral parts of the housing elements 26. Each of the radial formations 40 includes a recess or window 42 which opens laterally in the same direction as the housing element itself. Stops 44 close the recess 42 in the opposite direction as is well shown in FIG. 7. In addition, each recess 42 is provided with opposed grooves 46, best seen in FIG. 5; and these grooves slidably receive the edges of a plate member 48. Considering FIG. 5 in conjunction with FIG. 7, it will be appreciated that the plate member 48 is received in the recesses 42 of both housing elements 26 and spans the juncture therebetween thus locking these elements against relative rotational movement. Because of the placement of the formations 40 generally radially of the housing elements 26, these formations are in position for ready access. Hence, it has proved advantageous to mount terminal brackets 50 on the plate member 48 whereby to define a terminal board. Rivets 52 may be employed in so mounting the terminal brackets 50 in compliance with the showing of FIG. 5.

In compliance with an important feature of the invention, the drive shaft assembly 14 is arranged for adjustment in position of the drive shaft with facility and from either the front or the rear of the transformer unit. Structurally, the rotating contact assembly is arranged to carry all of its component parts in a captive unit which is independent of the drive shaft and which remains in adjusted position undisturbed during changes or adjustments of the shaft itself. More specifically and with reference to FIGS. 3-5, the drive shaft assembly 14 will be seen to comprise an upper hub support 54, an insulative driving hub 56, a contact arm unit 58, a knob shaft or drive shaft 60, a conductive spring Washer 62 and a bushing 64. The driving hub 56 defines an enclosure and is intended to be nonrotatably mounted relative to the contact arm unit 58. Accordingly, the driving hub 56 is fashioned with a square head or collar 66 and a cylindrical stem 68. Cooperatively, the contact arm unit 58 includes a folded, electrically conductive metal arm 70 that is fashioned with a generally square aperture 72 in one of its folded portions and a generally circular aperture 74 in the adjacent folded portion. The aperture 72 is sized and shaped to receive the square collar 66 fittedly, and the aperture 74 is sized and shaped to pass the stem 68 slidably. Completing the contact arm unit 58 is a tongue 76 which fittedly enters a cooperatively shaped slot 78 that is fashioned in a laminated carrier body 80. The carrier body 80 is also provided with a slot 82 that receives a conductive element or contact 84 in a slidably forceable manner. The conductive element 84 constitutes a wiper contact which bears on a track portion 86 of the winding 22 in compliance with the showing of FIG. 5; and the slidable fit of the contact 84 in the slot 82 permits easy replacement when the contact becomes Worn. The insulation is ground or otherwise abraded from the wire of the winding 22 in forming the track portion 86; and as is well known, this track portion may be plated with rhodium or other suitable metal in order to improve the electrical connections with the contact 84 and in order to improve wear resistance.

In addition, the bushing 64 is intended to be received in the driving hub 56 for rotatable and limited axially slidable movement. Continuing with reference to FIG. 5 and with additional reference to FIGS. 4 and 6, the bushing 64 is seen to be provided with a circumferential, external groove 88 adjacent one end. A discontinuous or C-ring retainer 90 is fitted in this groove to extend radially outwardly of the body of the bushing for purposes which will be made apparent hereinbelow. cooperatively, the driving hub 56 is fabricated as a pair of split shells 92, which are fashioned, in turn, with complemental, semicircular recesses 94 and a coaxial bore 96. The bore 96 is sized to receive the plain end of bushing 64 slidably and rotatably whereas the recesses 94 cooperate to define a cylindrical cavity which admits the retainer 90 and permits it a limited axially slidable movement therein. If desired, an augmenting, continuous washer element 98 may be situated loosely encircling the bushing 64 beneath the ring retainer to be disposed within the recesses 94 for further restricting the axially slidable movement of the bushing relative to the driving hub 56. The two shell halves of the driving hub are fashioned with an external groove which receives a C-ring retainer 100, retainer 100 serving to hold the driving hub about the plain end of the bushing.

To fix the knob shaft 60 relative to the driving hub 56, a metallic frame member 102 of U-shaped section and generally hexagonal silhouette is fitted into a cooperatively shaped recess 104 formed in the shell halves 92 of the driving hub. A set screw 106 passes freely through a bore 108 in one of the shell halves 92 to threadly enter a perforation in the frame member 102 for aggressive engagement with the knob shaft 60 whereby to hold the knob 60 in axial position relative to the driving hub, the contact arm unit 58 and the bushing 64. The knob shaft 60 passes slidably and rotatably through the central bore of the bushing to have a manual operating knob 110 afiixed to its opposite end whereby to permit rotation of the contact arm unit in compliance with the position of the manual knob 110. A set screw 112 conveniently fastens the manual knob to the shaft 60 as is shown in FIG. 5. It will be noted, with reference to FIG. 4, that the shaft 60 is of uniform, non-round section. Accordingly, it may be manufactured by the economical extrusion process and need not be milled.

The bushing 64 is also intended for non-rotatable mounting relative to the upper hub support 54; and for this purpose, the bushing 64 is provided with a medially disposed, male element 114 of hexagonal silhouette. Cooperatively, the hub support 54 includes an insulative bushing portion 116 and an insulative flange portion 118, the bushing portion 116 freely entering the central bore of the core and winding assembly 12 and being provided with an internal, female element 120 comprising a hexagonal recess for fitted receipt of the male element 114 as is well illustrated in FIG. 5. Non-rotatable mounting of the hub support 54 relative to the core and winding assembly 12 is achieved by means of a pair of ecccntrically disposed ears 122 which are mounted on an insulative radial arm 124, arm 124 rising integrally from the flange 118. A cooperatively shaped recess 126 is provided in an end section extension of each of the formations 40 as is shown in FIG. 2. A recess 126 fittedly receives the ears 122. The radial arm 124 also carries a conductive arm or strap 128 which defines a center lead, and this strap is positioned by spaced ribs 130 formed at the edges of the arm 124. The strap 128 merges to form a slip ring portion 132 surrounding the central bore in the upper hub support 54, and electrical contact between this slip ring portion and the conductive contact arm 58 is insured by the conductive spring washer 62 which is formed accordingly from some suitable material such as for example phosphor bronze or beryllium copper. Contact arm 58 incorporates a stop 133 which engages the ribs 130 to limit the rotation of the contact arm.

Continuing now with reference to FIG. 5, the dial and mounting plate assembly 16 is intended to cooperate with the bushing 64 of drive shaft assembly 14 in securing the drive shaft assembly in axial position relative to the core and winding assembly 12. For this purpose, the assembly 16 includes an insulative mounting plate 134; and this mounting plate is provided with a central boss 136 which fits rather loosely in the bore of the core and winding assembly 12 opposite the bushing 116 of the upper hub support 54. As is shown in FIG. 3, projections 138 are raised from the same side of the mounting plate 134 as the boss 136; and these projections present the same configuration as the ears 122 in order to fit into the confronting recess 126 of the core and winding assembly 12, the projections 138 being separated to admit an overvoltage input lead 140 therebetween. The lead 140 is connected between the one of the terminal brackets 50 and a medial turn of the winding 22, as is shown in FIG. 3. The boss 136 also has a central bore 142 which is sized to pass both the bushing 64 and the knob shaft 60 in compliance with the showing of FIG. 5. Specifically, the bushing 64 is provided with a threaded end 144; and this threaded end passes through the central aperture in the boss 136 to receive a cooperatively threaded nut 146. A lock washer 148 may be situated between the floor of boss 136 and the nut 146 to enhance the security of the fastening.

In addition to the manual knob 110 and the mounting plate 134, the dial and mounting plate assembly 16 includes a dial plate 150 having suitable graduations and indicia marked thereon in compliance with the showing of FIG. 1. The dial plate 150 is provided with a central aperture 152 which passes both the threaded end of bushing 64 and the knob end of shaft 60. The dial plate 150 is also fashioned with an eccentric hole 154 which receives a positioning post 156 that is raised from the confronting surface of mounting plate 134. With reference to FIG. 5, a nut 158 is readily threaded over the end of bushing 64 to hold the dial plate in position; and in use, it has proved advantageous to situate the panel board to which the transformer unit is to be mounted between the dial plate 150 and the mounting plate 134, after appropriately perforating the panel for the various protrud ing elements.

With the transformer unit once assembled and appropriately mounted, axial repositioning of the shaft 60, or complete replacement of that shaft together with the operating knob 110 is achieved merely by loosening the set screw 106; and for ready access to this set screw, the folded contact arm 70 is perforated with an access port 160, shown in FIGS. 3 and 5. As will be recognized, such manipulations of the drive shaft are readily accomplished without disturbing any of the rest of the structure. Considerable convenience and facility in the use of the transformer unit is thus presented. This convenience is also augmented by the aforementioned ease withwhich the wiping contact can be replaced. Moreover, it will be recognized that complete assembly of the transformer unit 10 can be achieved without reliance upon wet assembly operations or special tools or manufacturing equipment, simple keyed and threaded mechanical fastenings producing complete assembly of the unit.

The manner in which the present invention may be practiced and the purposes to which it may be put are believed evident from the foregoing descriptions.

The specific example herein shown and described is therefore to be considered as being primarily illustrative. Various changes in structure will, no doubt, occur to those skilled in the art; and such changes are to be understood as forming a part of this invention insofar as they fall within the spirit and scope of the appended claims.

The invention is claimed as follows:

1. In a variable transformer, the combination comprising: an annular magnetic core; an electrical winding on said core; insulation means fixed between said core and said winding; radially extending contact arm means mounted for movement in an angular path and including a conductive element carried in electrical contact with said winding, said contact arm means further having a nonround aperture generally aligned with the central axis of said core; mounting means for coupling said contact arm and means on said core and winding, including hub support means, first positioning means fixing said hub support means against rotational movement relative to said core and winding, bushing means, second positioning means non-rotatably mounting said bushing means to said hub support means, enclosure means having a non-round portion fittedly engaging the aperture of said contact arm means and including parts capturing means receiving an end portion of said bushing means for rotatable and limited axially slidable movement; drive shaft means slidably and rotatably disposed in said bushing means; and selectively operable fastening means acting to secure said drive shaft means to said parts capturing means, whereby to permit axial repositioning of said shaft means without disturbing the relative positions of said contact arm means and said winding.

2. In a variable transformer, the combination according to claim 1 wherein said first positioning means comprises interfitting, non-round protuberances and cooperatively shaped apertures on said support means and said insulation means.

3. In a variable transformer, the combination accord ing to claim 1 wherein said second positioning means comprises male and female means on said hub support means and said bushing means.

4. In a variable transformer, the combination according to claim 1 wherein said shaft means is of uniform, non-round cross-section.

5. In a variable transformer, the combination according to claim 1 wherein said parts capturing means comprises split shell elements and a resilient ring holding said split shell elements in assembled relationship.

6. In a variable transformer, the combination according to claim 1 wherein said contact arm means includes a carrier formation having a contact-receiving recess sized to accept said conductive element in slidably forceable relationship therein.

7. In a variable transformer, the combination comprising: an annular magnetic core; an electrical winding on said core; an insulative housing between said core and said winding, including a pair of cup-like housing elements aligned with their open ends in confronting relationship to form an enclosure for said core; radially extending contact arm means mounted for movement in an angular path and including a conductive element carried in electrical contact with said winding, said contact arm means further having a non-round aperture generally aligned with the central axis of said core; mounting means for coupling said contact arm means to said core and winding, including hub support means, first positioning means fixing said hub support means against rotational movement relative to said core and winding, bushing means, second positioning means non-rotatably mounting said bushing means to said hub support means, enclosure means having a nonround portion fittedly engaging the aperture of said contact arm means and including parts capturing means receiving an end portion of said bushing means for rotatable and limited axially slidable movement; drive shaft means slidably and rotatably disposed in said bushing means; and selectively operable fastening means acting to secure said drive shaft means to said parts capturing means, whereby to permit axial repositioning of said shaft means without disturbing the relative positions of said contact arm means and said winding.

8. In a variable transformer, the combination comprising: an annular magnetic core; an electrical winding on said core; a rigid insulating housing between said core and said Winding, including a pair of cup-like housing elements aligned with their open ends in confronting relationship to form an enclosure for said core, each of said housing elements having an annular base plate, a first tubular wall extending from said base plate at its outer edge and a second tubular wall extending from said base plate at its inner edge in coaxial relationship with said first tubular wall, said tubular walls and said base plate cooperating to define an encasement totally enclosing one end of said annular core; radially extending contact arm means mounted for movement in an angular path and including a conductive element carried in electric contact with said winding, said contact arm means further having a non-round aperture generally aligned with the central axis of said bore; mounting means for coupling said contact arm means to said core and winding, including hub support means telescopingly entering a said second tubular wall, first positioning means fixing said hub support means against rotational movement relative to said core and winding, bushing means, second positioning means non-rotatably mounting said bushing means to said hub support means, enclosure means having a non-round portion fittedly engaging the aperture of said contact arm means and including parts capturing means receiving an end portion of said bushing means for rotatable and limited axially slidable movement; drive shaft means slidably and rotatably disposed in said bushing means; and selectively operable fastening means acting to secure said drive shaft means to said parts capturing means, whereby to permit axial repositioning of said shaft means without disturbing the relative position of said contact arm means and said winding.

9. In a variable transformer, the combination according to claim 8 wherein each of said housing elements further includes a radial formation having a recess opening in the same direction as said housing elements and closed in the opposite direction, said recess having pposed grooves for slidably receiving a plate member, which further com-prises a plate member in the recesses of both of said housing elements spanning the juncture therebetween and locking said elements against relative rotational movement, and wherein part of said first positioning means is located on a said radial formation.

10. In a variable transformer, the combination comprising: an annular magnetic core; an electrical winding on said core; a rigid insulative housing between said core and said winding, including a pair of cup-like housing elements aligned with their open ends in confronting relationship to form an enclosure for said core, each of said housing elements having an annular base plate, a first tubular wall extending from said base plate at its outer edge and a second tubular wall extending from said base plate at its inner edge in coaxial relationship with said first tubular wall, said tubular walls and said base plate cooperating to define an encasement totally enclosing one end of said annular core, each of said housing elements further having a radial formation including a recess opening in the same direction as said housing element and closed in the opposite direction, said recess having opposed grooves for slidably receiving a plate member; a plate member in the recesses of both of said housing elements spanning the juncture therebetween and locking the said elements against relative rotational movement; radially extending contact arm means mounted for movement in an angular path and including a conductive element carried in electrical contact with said winding, said contact arm means further having a nonround aperture generally aligned with the central axis of said core; mounting means for coupling said contact arm means to said core and winding, including hub support means telescopingly entering said second tubular wall, first positioning means fixing said hu'b support means against rotational movement relative to said core and winding and comprising interfitting non-round protuberances and cooperatively shaped apertures on said support means and on one of said radial formations, bushing means, second positioning means non-rotatably mounting said bushing means to said hub support means and comprising male and female means on said hub support means and said bushing means, enclosure means having a non-round portion fittedly engaging the aperture of said contact arm means and including parts capturing means receiving an end portion of said bushing means for rotatable and limited axially slidable movement, said parts capturing means comprising split shell elements and a resilient retainer ring holding said split shell elements in assembled relationship; drive shaft means slidably and rotatably disposed in said bushing means; and selectively operable fastening mean acting to secure said drive shaft means to said parts capturing means, whereby to permit axial repositioning of said shaft means without disturbing the relative positions of said contact arm means and said Winding.

References Cited by the Examiner UNITED STATES PATENTS 2,985,857 5/1961 Ellin et al 336-148 3,185,948 5/1965 Helberg 336-148 X LEWIS H. MYERS, Primary Examiner.

L. E. ASKIN, Examiner. T. J. KOZMA, C. TORRES, Assistant Examiners. 

1. IN A VARIABLE TRANSFORMER THE COMBINATION COMPRISING: AN ANNULAR MAGNETIC CORE; AN ELECTRICAL WINDING ON SAID CORE; INSULATION MEANS FIXED BETWEEN SAID CORE AND SAID WINDING; RADIALLY EXTENDING CONTACT ARM MEANS MOUNTED FOR MOVEMENT IN AN ANGULAR PATH AND INCLUDING A CONDUCTIVE ELEMENT CARRIED IN ELECTRICAL CONTACT WITH SAID WINDING, SAID CONTACT ARM MEANS FURTHER HAVING A NONROUND APERTURE GENERALLY ALIGNED WITH THE CENTRAL AXIS OF SAID CORE; MOUNTING MEANS FOR COUPLING SAID CONTACT ARM AND MEANS ON SAID CORE AND WINDING, INCLUDING HUB SUPPORT MEANS, FIRST POSITIONING MEANS FIXING SAID HUB SUPPORT MEANS AGAINST ROTATIONAL MOVEMENT RELATIVE TO SAID CORE AND WINDING, BUSHING MEANS, SECOND POSITIONING MEANS NON-ROTATABLY MOUNTING SAID BUSHING MEANS TO SAID HUB SUPPORT MEANS, ENCLOSURE MEANS HAVING A NON-ROUND PORTION FITTEDLY ENGAGING THE APERTURE OF SAID CONTACT ARM MEANS AND INCLUDING PARTS CAPTURING MEANS RECEIVING AN END PORTION OF SAID BUSHING MEANS FOR ROTATABLE AND LIMITED AXIALLY SLIDABLE MOVEMENT; DRIVE SHAFT MEANS SLIDABLY AND ROTATABLY DISPOSED IN SAID BUSHING MEANS; AND SELECTIVELY OPERABLE FASTENING MEANS ACTING TO SECURE SAID 